1. Field of the Invention
This invention relates to the field of ammunition, more specifically, to non-lethal ammunition used in training and war games that could also be used in automatic and semi-automatic firearms.
2. Description of the Related Art
There has long existed the need for firing practice of automatic and semi-automatic firearms. As automatic firearms are used by more and more organizations such as the military and police, the need for an effective practice has grown urgently. The ideal practice round for automatic and semi-automatic weapons incorporates the functions of firing a non-lethal projectile to mark the impact point, satisfactorily actuating the automatic ejection of the spent casing, functioning in a standard firearm with a minimum modification, and being relatively inexpensive.
The primary problem that has existed in using automatic or semi-automatic firearms is the providing of enough xe2x80x9ckickbackxe2x80x9d without raising the muzzle velocity or impact force of the projectile. Usually with practice or non-lethal rounds it is important to maintain lower muzzle velocities and keep weight, and therefore to reduce the inertia of the projectile, at a minimum. However, under such circumstances, usually such rounds have not provided enough back force for automatic ejection mechanism for proper actuation.
Practice firearms nowadays being used involve those utilizing a laser, CO2 actuation or blanks. Obviously, the laser type devices are expensive, somewhat cumbersome, and usually are not conventional in operation. CO2 type practice devices are sometimes actuating a capsule type of cartridge with high-pressurized gas and are usually not conventional in operation. The firing of blanks obviously involves no projectile to mark the point of impact and thus are unable to offer the advantage of the conventional firearms during practice.
However, during the ballistic cycle of ammunition, the operation of conventional automatic and semi-automatic firearms are actuated either by the expansion of propellant gas against a sabot connected to the recoiling bolt or by direct blowback of the cartridge case against the bolt upon expansion of the propellant gas. In these systems, the energy provided to the recoil mechanism is related to that imparted to the projectile. That is, a reduced pressure in the chamber or variations in weight of the projectile will result in variation of the total energy given to the firearm-operating mechanism which, in turn, will affect its cyclic rate or the reliability of its operation. With low-mass projectiles or the type used in training and non-lethal cartridge, the problem is especially severe. Frangible projectiles may not be capable of withstanding high accelerations. The low energy required for launch of these lightweight projectiles may not produce a sufficient reaction or necessitate a high enough chamber pressure to cycle conventional firearm mechanisms. Blank cartridge, that is, a cartridge without a projectile, will not normally be able to automatically cycle ejection without a muzzle adapter to increase the pressure in the system sufficiently to make the mechanism function.
The above mentioned problem may also be observed in larger caliber guns, such as 40 mm grenade launchers, where a relatively low-velocity projectile with limited capacity to withstand high accelerations, is launched from an automatic gas-operated firearms. To overcome such problems, the xe2x80x9chigh-lowxe2x80x9d ballistic system is adopted. Propellant in the xe2x80x9chigh-lowxe2x80x9d ballistic system is initially burned in a high-pressure section of a partitioned cartridge case and released through orifices into the side containing the projectile at a rate sufficient to limit the peak pressure or acceleration on the projectile. Such a system is described in U.S. Pat. No. 4,686,905. While such system can provide reduced peak forces available for firearm function, necessitating design compromises in the firearm.
U.S. Pat. No. 5,359,937 entitled xe2x80x9cReduced Energy Cartridgexe2x80x9d, issued to Dittrich on Nov. 1, 1994, disclosed a cartridge for low-mass, frangible projectile which comprises a sabot to propel against an inner shoulder of a chamber. The cartridge has a sabot with an orifice applied to lead the propellant gas from the rear of a sabot to the rear of a projectile in order to eject the projectile under controlled impact force. The wall of the cartridge case has an inwardly extended flange and the bottom of the sabot has an outward step. Upon percussion, the cartridge case is pushed backward opposite the sabot by expansion of propellant gas and the step of the sabot is engaged with the flange of the case to engage the cartridge case together with the sabot, thus enables the spent sabot and the cartridge case to eject together. However, during assembly, because the outer diameter of the step of the sabot is larger than the inner diameter of the flange of the case, the sabot is unable to be inserted into the case directly. Other than extra finishing process, material with good malleability, such as copper is necessary for the cartridge case in order to insert the sabot smoothly into the case during assembling.
It is the primary object of the present invention to provide a practice cartridge which can launch a low-mass, frangible, non-lethal or low energy projectile and the cartridge can be produced efficiently and the material is not limited to conventional copper material, hence to reduce the production cost.
It is still another object of the present invention to provide a practice cartridge which can launch a low-mass, frangible, non-lethal or low energy projectile and the cartridge can be used in existing semi-automatic and automatic firearms to maintain their reliability of cycling mechanism in semi-automatic and automatic firearms.
The above-mentioned objects of the invention are achieved by the provision of a cartridge used in existing firearms, such as semi-automatic and automatic firearms, to launch a low-energy projectile. The cartridge comprises a cartridge case having a rear-end portion and a front-end portion, the front-end portion defining an inner diameter and its inner side-wall having an inclined groove; a primer disposed in the bottom of the cartridge case; a sabot comprising a front-end portion with a greater diameter and a rear-end portion with a smaller diameter, the rear-end portion having a substantially occlude end, wherein the outer diameter of the rear-end portion is substantially the same as the inner diameter of the inner wall of the cartridge case fitted hermetically into the cartridge case forming a hermetic space therein, and the outside of the rear-end portion is provided with a groove. The front-end portion of the sabot may be propelled against the shoulder of the chamber and the rear-end portion has at least an orifice to connect the hermetic space to the front-end portion allowing the propellant gas within the hermetic space bleed to the front-end portion through the orifice. Also a limiting element is disposed in the groove of the sabot. Upon percussion, as the inclined groove of the cartridge case slides towards the limiting element, due to the elasticity, the limiting element returns to its uncompressed state and engages with the inclined groove of the cartridge case, thereby limiting the further movement of the cartridge case relative to the sabot.
According to the cartridge of the present invention, during assembly, the limiting element disposed in the groove of the sabot is fitted into the cartridge case. As the limiting element passes through the inclined groove in the cartridge case, it extends into the inclined groove due to the elasticity. However, as the inclined groove has an inwardly inclined surface, the limiting element can be compressed into the groove by the inclined surface. Thus the sabot can further enter into the cartridge case until the step of the sabot is propelled against the cartridge case. Therefore, the cartridge of the invention can overcome the limitation on manufacture and materials described on U.S. Pat. No. 5,359,937.
Upon percussion, the propellant gas bursts from the hermetic space through the orifice to the rear-end portion of the projectile to eject the projectile. The front-end portion of the sabot is propelled against the shoulder of the chamber, therefore the cartridge case is pushed backward by the expanded gas generated from the powder. As the inclined groove of the cartridge case slides toward the limiting element, due to the elasticity, the limiting element returns to its uncompressed state and engages with the inclined groove of the cartridge case. Thereby it limits the further movement of the cartridge case relative to the sabot to ensure the spent sabot and the cartridge case to be ejected together in order to achieve the aim of cycling the automatic and semi-automatic firearms.